Silencer for moving picture booths



w. s. BOGGS SILENCER FOR MOVING PICTURE BOOTHS July 9, 1935.

Filed April 19, 1954v SILENCER. ron MOG no Wilber Smith Boggs, Las Animas, Colo.

Application April 191 1934, Serial No. 721,347

6 Claims.

This invention relates to improvements in silencers for moving picture booths.

In moving picture theaters it is always desirable to prevent sounds that originate in the projection booth from entering the auditorium, as such sounds are disturbing to the audience and this is more especially true since the advent of the sound pictures. Moving picture projecting apparatus makes considerable noise and since an opening must be provided in the wall so as to permit the light beam to enter the auditorium and project the picture onto the screen, such noises will invariably enter the auditorium unless precautions are taken to prevent it.

In smaller moving picture theaters the noises from the projection booth will cause a greater disturbance than in larger theaters for the reason that in the latter, the projection booth is usually removed a long distance from the audience and is located very high, with the result that noises that pass through the opening will be dissipated before they reach the audience.

The objection referred to above has been recognized and in some instances the opening through which the light passes from the projection apparatus to the screen is closed by means of a piece of plate glass which serves to some extent, to prevent the transmission of sound, but which, in itself, is objectionable for the reason that it cuts down the amount of light to quite an appreciable extent and unless the glass is kept scrupulously clean, the light reduction becomes highly objectionable.

Another objection to having a glass closure is that flies and other insects frequently light on the glass and will be projected in silhouette on zhe screen which detracts greatly from the picure. t

It is the object of this invention to produce a silencer that can be applied to the wall of the projection booth and which is provided with an opening that is placed into register with the opening in the booth so that the beam of light from the projection machine will pass through the booth wall and through the silencer without having to pass through any glass or other closure that tends to decrease the amount of light projected.

This invention, briefly described, consists of a tubular member, which may be circular in cross section, or of any other cross sectional shape, and which is provided on its inner surface with a plurality of flanges that project inwardly and the openings in which are graduated so as to form a tubular passage of substantially the same shape and size as the beam of light from the projection machine at the particular point where it passes through the silencer. The silencer is secured to the outside or to the inside of the projection booth wall and permits unobstructed passage for the light but serves to break up any sound waves that may enter the same.

Having thus briefly described theinvention, the same will now be described in detail, and for this purpose reference will be had to the accompanying drawing in which the preferred embodiment thereof has been illustrated, and in which:

Fig. l is a vertical section through a projection booth showing a projection apparatus in place inside of the booth and the improved silencer secured to the outer surface of the booth wall;

Fig. 2 is a section through a silencer of a slightly different shape than that illustrated in Fig. 1;

Fig. 3 is a section through a silencer showing a slightly different form; and

Fig. 4 is a transverse section taken on line d-fl, Fig. 2.

In the drawing reference numeral 5 designates the floor of a projection booth and reference numeral 6 indicates the projection machine. The lens has been indicated by reference numeral 1, while the screen has been designated by reference numeral 8. When the machine is in operation a light beam like that indicated by reference numeral 9 is projected from the machine onto the screen and this beam has the shape of a cone whose ex lies'within the projection apparatus and wh se base is formed by the surface of the screen. The front wall of the projection booth has been indicated by reference numeral l0 and this is provided with an opening I I through which the light bean passes. As above described the opening ll serves not only to let the light pass through from the booth into the auditorium, but it also permits sound waves to enter the auditorium.

In order to prevent sound waves from entering the auditorium, a silencer is applied to the booth wall in the manner shown in the drawing. This silencer is usually so formed that the outer wall 45 thereof, which has been designated by reference numeral I2, is cylindrical and secured at one end to a base l3. Secured to the inner surface of the tubular cylindrical wall are a number of rings l4 that are each provided with an opening l5. The 50 openings in the rings are preferably graduated in size so as to be progressively larger away from the camera and thus result in an opening of frusto-conical shape, which is preferably so designed that its inclination corresponds to that 55 of the light beam. The base I3 is also provided with an opening as shown in the drawing. When sounds originating in the moving picture booth pass through the opening ll into the interior of the silencer, the inwardly projecting flanges serve to break up the sound waves with the result that they do not enter the auditorium.

In Fig. 1 the outer wall I2 has been shown as cylindrical, but it can be any other suitable shape and in Fig. 2 the wall I2a has been shown as having a frusto-conical surface. The object of making it frusto-conical is to make the rings it that form the flanges all of the same width from the center opening to the periphery of the rings. In the modification shown in Fig. 2, the base i3 is at an angle to the axis of the frusto-conical member l2a so as to make the opening through which the light passes'symmetrical with respect to the outer surface of memberlZa. Since the booth walls are perpendicular and the light beam always points downwardly, the construction shown in Fig. 2 1s believed to be preferable to that shown in Fig. 1.

In Fig. 3 the outer surface l2b is the surface of a rectangular truncated cone and is suitable for places where the center of the screen is at the same level as the lens of the projecting apparatus.

It will be observed from the several modifications on the drawing that the common feature is the tubular outer members l2, i2a, iZb which are provided on their inner surfaces with a plurality of inwardly extending flanges having openings whose diameters increase progressively the booth to the auditorium through which a conical light beam may pass. Such flanges serve to break up the sound waves and. to prevent them from traveling from the booth to the auditorium with the result that the auditorium is not subjected to any disturbance due to noises originating within the sound booth.

Attention is called to the fact that the volumes of the annular channels between the several flanges increases progressively from one end of the silencer to the other. It is immaterial in what direction this increase takes place as it is only necessary that the air in each channel shall respond to a different frequency.

Special attention is called to the fact that there is no obstruction for the light beam as no glass is used, but on the other hand the opening extends from the insideof the booth to the inside of the auditorium in such a way as to permit the light to pass freely from the machine to the screen.

Experiments have shown that the combination with the wall of a projecting booth of a silencing device like that shown is very satisfactory for the purposes intended.

The above described silencer is of a very simple construction and is preferably made from some material formed from coarse vegetable fiber as these have shown a special suitability forsound insulation. The width of the flanges from the opening to the inside of the tubular member can vary within wide limits and the proportion shown in the drawing is not to be considered as a limitation affecting the invention.

Having described the invention what is claimed as new is:

1. A silencer for preventing sounds from'passing through an opening in the partition wall between a moving picture projection booth and the auditorium of a moving picture theater, comprising an elongated tubular member having a plurality of spaced annular flanges extending around the axis of the opening, the openings in the flanges increasing in diameter progressively from one end of the silencer to the other end whereby a plurality of channels of different volumes and periods of vibration are formed which serve to break up the sound waves.

2. A silencer for preventing sounds from passing through an opening in the partition wall between a moving picture projection booth and the auditorium of a moving picture theater, comprising an elongated tubular member having a plurality of spaced annular flanges made from compressed vegetable fibers and which flanges extend around the axis of the opening, the openings in the flanges increasing in diameter progressively from one end of the silencer to the other end whereby a plurality of channels of different volumes and periods of vibration are formed which serve to break up the sound waves.

3. In a moving picture theater having an auditorium and a projection booth in which the projection apparatus is located, the wall of the booth having an opening for the passage of the light beam from the projection apparatus, means for breaking up sound waves originating within the booth and for preventing them from entering the auditorium, said means comprising a tubular member having a clear constantly unobstructed opening which is surrounded by spaced ring-like members of fibrous material arranged in parallel planes perpendicular to the axis of the opening so as to form depressed annular channels that serve to break the sound waves.

4. A silencer for preventing sounds from passing through an opening in the partition wall between a moving picture projection booth and the auditorium, comprising a frusto-conical tubular member, having a plurality of spaced annular flanges extending around the axis of the opening, whereby a plurality of channels of difierent volumes are formed which serveto break up the sound waves.

5. A silencer for preventing sounds from passing through an opening in the partition wallbetween a moving picture projection booth and the auditorium, comprising a tubular member havin a plurality of spaced annular flanges which flanges extend around. the axis of the opening, the openings in the flanges increasing in diameter from one endof the, silencer to the other end,

whereby a plurality of channels of different volumes are formed which serve to break up the sound waves.

6. In combination an auditorium adapted for the reproduction of sound pictures, a projection booth adjacent said auditorium and separated therefrom by a sound enclosing wall, an aperture in said wall for the projection of picture images therethrough, and means surrounding said aperture and extending along the axis of projection for absorbing sound tending to be emitted through the aperture, said means provided with a plurality of spaced interior flanges having a clear constantly unobstructed opening through the same, whereby a plurality of channels or depressions are formed between the flanges which serve to break up the sound waves.

WILBER SMITH BOGGS. 

